Technologies for producing ethanol and the like by saccharifying woody biomass or other biomass using dilute sulfuric acid or concentrated sulfuric acid, subsequently subjecting the resultant saccharides to solid-liquid separation, neutralizing the liquid phase, and utilizing the resultant components as raw materials for ethanol fermentation or the like, have been hitherto put to practical use (Patent Literature 1 and Patent Literature 2).
Furthermore, production of industrial chemical raw materials (for example, lactic acid fermentation) using saccharides as staring raw materials have been also considered.
The term biomass as used herein refers to a living organism, or accumulation of organic materials derived from living organisms, that has been incorporated into the material circulation system of the global biosphere (see JIS K 3600 1258).
Here, sugarcane, corn and the like that are currently used as alcohol raw materials have been originally used for food. However, using these food resources stably as long-term industrially utilized resources is not preferable from the viewpoint of the life cycle of valuable foods.
For this reason, it is an important challenge to efficiently utilize cellulosic resources such as herbaceous biomass and woody biomass, which are considered as potentially useful resources.
Furthermore, cellulosic resources have compositions varying from 38% to 50% of cellulose and from 23% to 32% of hemicellulose components, and also include lignin components, which are not used as fermentation raw materials, at a proportion varying from 15% to 22%. Due to the research on industrialization with many problems still remaining unsolved, raw materials are assumed to be fixed, and under the current situation, no technologies have been disclosed on production systems that take into consideration of the diversity of raw materials.
Furthermore, since it is contemplated to aim at providing countermeasures against garbage problems, global warming and the like with raw materials which are more disadvantageous as fermentation raw materials than starch raw materials, production systems involving fixed raw materials have almost no meaning. A production system is useless if it is not applicable to a wide variety of general waste materials. It is the current situation that enzymatic saccharification methods are also considered to be poorly efficient per se and pose problems to be solved in the future. The saccharification ratio obtainable by acid treatment also has a small value of approximately 75% (on the basis of components that can be saccharified), due to excessive decomposition of saccharides caused by excessive reaction, and the like. Therefore, the ethanol production yield remains only at approximately 25% based on cellulosic resources (Patent Literature 3).
In the prior art technologies of Patent Literatures 1 to 3, there has been a phenomenon in which side reaction products cause inhibition of enzymatic saccharification, and the saccharide yield is decreased. Therefore, hydrothermal decomposition apparatuses that eliminate enzymatic saccharification inhibiting materials and increase the enzymatic saccharifiability of cellulose main constituent, have been previously suggested (Patent Literatures 4 to 7).